On the geothermal action, organic matters in a stratum firstly generate crude oil, and if the temperature further rise, the crude oil will crack to generate natural gas. During the process of the crude oil changing into the natural gas, the gas can flow out of interspaces or crannies of rock, continuously or intermittently, due to continuous increasing of the gas pressure, while the un-cracking crude oil continues the cracking process at its original locations. In the research of oil and gas geochemistry, an experiment method is needed to research the cracking process of crude oil.
The existing manpower simulation experiment is much different from the natural geological conditions. At the natural geological conditions, the crude oil experience a very slow process with the lower temperature (less than 200° C.) and long time (from millions of years to hundreds of millions of years), and at such a lower temperature, the crude oil can maintain liquid and locally continue its cracking process. However, under the manpower simulation conditions, the time can not be too long (generally, from 2 to 20 days) and the reaction temperature, the range of which is typically 300° C. to 700° C., has to be increased in order to compensate the insufficiency of time. At such a high temperature, the crude oil has been boiled before cracking. In this case, if a reaction container is not closed, the boiled crude oil will escape from the container, which causes stop of the cracking process. For this reason, at present crude oil cracking experiments commonly use closed containers at home and abroad. That is, the container is not opened until the reaction is over, and after the reaction is over, the container is opened to remove the gas. However, this method apparently does not comply with the rule that the gas generated by cracking discharges continuously or intermittently.